Diabetic autonomic neuropathy is found with a high incidence in individuals with type 2 diabetes. More specifically, cardiac autonomic neuropathy (CAN) is the most common neuropathy found and is associated with an increase in ischemic heart disease and a higher incidence of arrhythmias and sudden death in obese and type 2 diabetic individuals. Nearly half of diabetic patients have CAN and if they do then the 5-yr mortality is substantially increased. Obesity alone compromises autonomic function, but in type 2 diabetics the hyperinsulinemic milieu is also speculated to further alter autonomic function potentially leading to the higher incidence of arrhythmias and sudden death in this population. Exercise and weight loss has been shown to improve CAN in obese individuals, but the reversibility of CAN in the type 2 diabetic individual is unclear. The purpose of this study is to determine if differences exist in CAN between obese non-diabetics and obese type 2 diabetic individuals, and if this response can be altered by 16 wk of aerobic exercise training. In addition we will also establish if gender differences occur with this response to training. We will recruit 40 men and women (40-60 yr) (20 obese/non-diabetics and 20 obese/ type 2 diabetics). Subjects will exercise train 4 days/wk at 65% V02 max. This study will train subjects in a supervised setting for the first month and then subjects will train in a supervised home-based program. Subjects will be monitored at home via phone, email and a website to track their progress. At the initiation and completion of the study, subjects will have their metabolic status (glucose and insulin levels (OGTT), blood lipids, HbA 1c) and autonomic function (heart rate variability-HRV) measured. This project is one of the first to determine if autonomic function can be improved in type 2 diabetics after participating in an exercise program, which is part of the current therapy. Because of the increased mortality in this population, this project will provide insight into whether autonomic dysfunction can be reversed and if gender differences occur in this response.